Reprint & Copyright c by/ A /- (Aerospace Medical Association, Washington, DC

qd*~E LE:C -f10 JAN 13 1987.

L0iM> A

< Comparison of Human Impact Response 'fnRestraint Systems With and Without a

SNegative G Strap

BERNARD F. HEARON, M.D , and JAMES W BRINKLEY, B S.

Air Force Aerospace Medical Research Laboratory, Wright-Patterson Air Force Base, Ohio

ItEARON BF. BRI%1CLEY 3W Comnp-is of hsursss impact ~NE INTENDED PURPOSE of a negative G strapresponse is restraint sysiert,sIt~h and without a neganse G3 strap 0J Is to prevent "--:.manining" or movement ofAvial Spame ltnoron Med 1986. 57 301-12-A test pragroan to assess; the influence of a neatv G stap the torso under the lap belt during forward-facing

on restraint dynamics and humnan impact response was candscteid. (- G.) impact accelerations By tethering the ;ap beltat APANMIL There wene 131 expenimental-levell i.mpacmt ests with to the forward portion of the seat, the negative Gvolunteer subjects performed in eight different test conafiddas. or crotch strap prevents the lap belt from riding upForviatd-fociitg -G.) aimpacts were carried out ani a hoiort and over the anterior superior iliac spines, pressingaccele~ratar. while vertical (+G,) impact tests were thes abdme an asn eo itravertical drop toweri facility. In bath axes. the expeimna againstth aboe an cusg nuqierl

eaasrewnoan approximate hfsine wvvesfo-i with p& injury At the Air Force Aerospace Medical Researchaclaiaupto 10 G and velocity change up to 9.2 V1~. Laboratory (AFAMRL), complete transection of the

Subjects wet, restrisned ta #he tost vehicle using either the PCU- rectus abdominus muscles and hepatic laceration have15/P torso harness andl lap belt, which is used patnayin ocreinnshtzdbaonubcsasheeulsuch aircraft as the A-20 and F-15, or a cavetina d curdinaetublebbonsbecsa hersl

shoulder stamp arnd lap belt conhiguration. In orhalofthe test of submarining dunrig high-acceleration -Gx impactscotdiditins, lined-lesngt neate G staswere. incrparated into (unpublished data) In the operational setting, suchthese restraint systeia n teahr test acondition's, theusnnadfld accelerations experienced by aircrew members duringrestraint systetnseweroe~voluated. Addfing the negative G strap aircraft crashes or during the aerodynamic deceleration

inldddcesn h edny oadsbaiigi owrl immediately following emergency ejections may produce

;farin iniactsi prsnidling better accupant-ea coupling dsaln similar injury patterns.fIe fa mllsn iniproving vertical impact protection. Su=cin The usefulness of crotch straps as anti-submariningbenefits aper to reutfa= use of the negative G ttrap ta devices was recognized by Stapp (21). who coin-warrant a reaanssdta its incorporaion int seltd ducted -. ipc xeiet ihhmnsbetUSA retra int systemss tsucht an th PC '-lf toso hares imatepeietnwtduansbe

>_ lop bltn. Addlitional data analysis reveled that th owtoo restrained by harness configurations with and withoutC abl shule stanIa etrstan uddbte antisubnsanning straps The high-acceleration trests ino owr-aigadvria mac rtsis hntePU1/ that study most frequently cited used two crotch straps,

tar> hans n a et olgrta..Fute eerha each attached to an adjacent rear corner of the seat andC-D mcA:AA.i lne oietf rsrmtýesfaue hc to the lap belt buckle to form an inverted-V When these

snJproecion spisethperfo- neo tna n uueipc straps were not incorporated into the restraint harness,L&*J ~ s~stemsubmarining was noted in some cases Stapp reported___ that -the forward motton of the shoulder- during impact

This nassapiwasrecessed teresmins sApri9- iTS herorsesd appltes traction to the shoulder straps, raising the lapmanuscispnt was acciptned for pubiicaiio in August 19f5 belt, permitting the lower halt of the body to begin

lnfonneid cossent %as prosided bsy atl subied participating in this bending around it The upper edge of the belt lodgestest progvan in accotidasce with the applicable humns sse guidelines agisthloemrinofheib t.aantteas, d~sednis AP 169-3 gis h oe agn fterb n gis h

Send reprinst reRqsesis to J W Brnkiley, AAMPLIJBBP. WPAFb. upper abdomen.-OH 45433 The second purpocse of a negative G strap is to

-6 1 2 2 9 0 37 A-iaso Spare. asd Psi ronmewsit.t edirse * Aprin. 1986 3011

NEGATIVE G STRAP EVALUATION-HEARON & BRINKLEY

provide better mechanical coupling between tie seat METHODSand its occupant during low-frequency flight vibrations,sustained -G. acceleration maneuvers, and adverse A controlled impact experiment using volunteeraircraft motions which may occur if the aircraft departs subjects was designed to meet these objectives Thefrom controlled flight This function of the tie-down test conditions investigated are summarized in Tablestrap is obviously more important than its role as an anti- I Testing was accomplished in two phases First,submanning device since sustained -G, accelerations test conditions A, B, C,. and D were completed oncausing the aircrew member to become "light- in he AFAMRL Horizontal Impulse Accelerator (HIA)the seat may be frequently encountered in day-to-day Then, test conditions E, F, G, and H were performedflight operations Inadequate -G, restraint degrades on the AFAMRL Vertical Deceleration Tower (VDT)ability to control the aircraft (1,15,18), cadses helmet- Experimental exposures of subjects during each phasecanopy contact (14,15), impairs abiity to eject in some of testing ..ere randomizedcircumstances (1,18), and predisposes to injury during Parametric analysis of matched test conditions per-ejection (5,15,18). Loss of aircraft and death of aircrew mitted the identification of response differences result-members have been attributed to the inadequate -G. ing from a single controlled variable, such as negative Grestraint provided by the United States Navy MA- strap or restraint harness configuration Eight separate2 integrated torso harness (1) Recently, a USAF comparisons among the test conditions were performedRF-4 pilot suffered a cervical vertebral fracture and These were grouped into four comparison sets (Tabletransient paralysis as a result of - G6induced helmet- 11) in order to simplify the presentation and discussioncanopy contact and cervical flexion during a subsequent of test results.+G. maneuver (19). The crewmember has a residual The volunteer subjects (20 men, I woman) wereneurologic deficit due to this incident active-duty officers and enlisted personnel at Wright-

Despite the ancedotal evidence and widespread Patterson Air Force Base. Prior to participation,support among the aeromedical community for use subjects were required to meet stature, weight, andof a negative G strap, an adequate experimental sitting height criteria for USAF pilots and to completebasis for recommending negative G strap incorporation a medical screening more rigorous than the USAFinto specific USAF restraint systems was lacking Flying Class II evaluation (6) The selection method,Therefore, AFAMRL in conjunction with the Life therefore, was designed to yield a subject sampleSupport System Program Office of the Aeronautical comparable to the USAF flying population in termsSystems Division initiated an investigation of the of age and anthropometry, but supranormal in termsfeasibility and effectiveness of adding a crotch strap to of susceptibility to impact injury Characteristics ofthe PCU-15/P torso harness and .ap belt, which is used the subject sample (means and standard deviations) arein aircraft equipped with the ACES II ejection scat summarized as follows: age, 25.9 ± 3 9 years; weight,such as the A-10, F-15. F-16, B-IB, and T-46A. The 76.2 ±- 9 8 kg; height 175 ± 7.2 cm, sitting height, 92.7research effort addressed one aspect of an ACES i1 ± 3.4 cmrestraint modification program undertaken in respoise To minimize the potential for injury to subjects,to a statement of operational need by the USAF Tactical the tests were conducted at presumed subinjury impactAir Command for improved restraint during sustained acceleration levels. In order to familiarize subjects with-G6 acceleration, out-of-control flight conditions, and the test procedures and equipment, orientation impactsemergency escape were performed prior to experimental-level exposures.

The primary objective of the present study was to For the forward-facing or horizontal test phase, 6-Gevaluate human response to forward-facing (-G.) and peak (6 7 m • s ') and 8-G peak (7.9 m • s') impactvertical (+G.) impacts in operational USAF restraint levels were chosen for subject orientation, and thesystems with and without a negative G strap Secondary experimental exposure level was 10-G peak (9.1 m" s ')objectives included comparing human impact response For the vertical test phase, the orientation exposurein the PCU-15/P torso harness and lap belt arrangement was 8-G peak (7.0 m - s-') and the experimentalto such response in a conventional double shoulder strap exposures were performed at 10-G peak (7.9 m - s-').and lap belt configuration and establishing performance All acceleration profiles %ere approximate half-sinebaseline data for use in guiding the development of new waveforms. The applied forces at the higher test levelsand improved restraint systems for advanced tactical were generally sufficient to overcome the forces offighter aircraft voluntary muscle contraction and. therefore, produced

TABLE I EXPERIMENTAL CONDFlIONS

"TEST CONDITIONDESIGNATION A B C D E F G H

TEST PHASE Honronial Honzonwia Honzonul Honzoenta Vertial Vertical Vertical VertcalRESTRAINT SYSTE.M PCU-15,1 PCU-iS/P Conventional Conentmnai PCU-15P PCU-15/PConv-enrional ConveetionalNEGATIVE G STRAP Absent Present Absent Present Absent Present Absent Present

Horizoniu (-G1) nimpacts were conducted on AFAMRL Impulse Accei'atorVertical (+ G) nmpacts -ere perfornmed on AFAMRL Vertical Deceleration Toncr

302 A-aaon. Spice. ind Ern tronmien Medicmn Apnil. 1986

NEGATIVE G STRAP EVALUATION-HEARON & BRINKLEY

TABLE II COMPARISONS OF MATCHED TEST CONDITIONS chamber pressures of the HIA actuator were identicalfor all experimental-level exposures The AFAMRL

NEGATIVE G STRAP EFFECTS VDT was used to perform the impacts in the vertical testWithout vs Wah phase The impact carnage of this facility moved along

Honzorucai (- G,) Tesis A (n = 14) B vertical rails and supported the test fixture, seat, and

C (n = 18) D restraint system The carnage was elevated to a dropheight of 3.35 m and allowed to free fall onto a hydraulic

Vertical (+ G,) Tests E (n = 16) F decelerator to produce the desired acceleration profile0 (n = 15) H The carriage drop height, the mass of the test fixture,

and the impact plunger were the same for all verticalRESTRAINT HARNESS EFFECTS tests to assure nearly identical impact conditions from

PCU-15/P vs Conventional test to testThe PCU-15/P torso/parachute harness (formerly

Horizontal (- G0) Tests A 1n i5) C known as the PCU-2/P) was used by most male subjectsB (n = 14) D during both phases of the test program (Fig. 1). The

Vertcal (- Gi) Tests E in = 14) G smaller male subjects and the female subject used theF (n = 16) H smaller size but otherwise identical PCU-16/P torso

harness. The shoulder straps, attached to the parachuten= number of matched pais (same subjects tested n both expen- riser and restraint fittings (Koch Part No 015-12231-mental conditions) 3) of the PCU-15/P harness, consisted of 4.5-cm wide

type I polyester webbing (MIL-W-25361) The lapa subject response suitable for comparative parametric belt used with the PCU-15/P torso harness was ananalysis HBU configuration consisting of 4.5-cm wide type Ii

The accelerator facility used for the horizontal test polyester webbingphase was the AFAMRL HIA (20) which operates on The second harness, used as a control or standard ofthe principle of differential gas pressure In order to comparison, was a conventional USAF double shouldermaintain constant impact test conditions, the pretest strap and lap belt configuration (Fig. 2) The shoulder

Fig. 1. P•I$/P fo,1i harrien and lap bob configuration used Fig. 2. Conventonal doubl- iiid, ra and lapboin toot co•'ndiin A and L. confguration L-zeI in test condiitims C and G.

Attation Space, and Enri-ommental Medicune'"Arn/, 1986 303

NEGATIVE G STRAP EVALUATION-HEARON & BRINKLEY

straps of this restraint were an adjustable type MB- seat. For the horizontal tests, the negative G strap was6 harness constructed of 4.5-crn wide type I polyester 25.4 cm in length; for the vertical tests, the negative Gwebbing, and the lap belt was an HBU configuration strap was 21 9 cm in length. The difference in theseconstructed of 4.5-cm wide type XIII nylon webbing lengths was because the seat pan was inclined 60 from(MIL-W-4088H) The lap belt of each harness was honzontal during the forward-facmng test phase, but itanchored at two locations, while the shoulder straps was not inclined during the vertical test phasewere anchored at a single location on the aft biiiihead Each subject was properly fitted with the PCU-15/Pof the test fixture. (or PCU-16/P) torso/parachute harness. In particular,

The negative G strap (USAF Part No 45402-0101649- the leg straps were adjusted in accordance with the01), added to the restraint harnesses in some test harness technical order so thit, when snug, the subjectconditions (Fig. 3 and 4), consisted of 4 5-cm wide type c',ild not assume the fully upright standing positionI polyester webbing In order to accommodate thz Afttr the subject was seated on the test fixture, theadded negative G strap, a modified type MA-t harriess lap belt and shoulder straps were pretcnsioned to 89buckle was used with each lap belt during all tests in 22 N, measured by load cells at the three attachmentthe series The crotch strap was anchored at a Foint fittings The tension of the fixed-length negative G38.1 cm forward of the seat reference axis This position strap could not be adjusted Subjects were instructed tocorresponds to the distance from the seat reference axis assume identical preimpact body positions prior to eachto the center of the forward edge of the ACES II survival test in the series, with head against the headrest whilekit hd and is consistent with accepted guidance (4) maintaining a mild-to-moderate amount of posterior"The length of the negative G strap used was selected cervical muscle tension and with arms resting on anteriorin a static evaluation of several straps of different thighs Subjects wore HGU-26/P flight helmets dunnglengths Subjects representative of the range of subject the vertical tests, but not during the forward-faong testsanthropometry in this study participated in the static to reduce the likelihood of cervical muscle strainevaluation The negative G strap chosen in each test The test fixtures, restraint harnesses, and subjectsphase best fulfilled the intended purpose of the strap, were instrumented to obtain pertinent data duringi e , tethering the lap belt to the forward portion of the each experiment. Measured parameters included

V.

FIg. 3. PCU-15/P torso harness and lap belt configaumilon with Fig. 4. Conventional double shoulder strap and lap beltan added negative Gsirp used in test c€ditions I and F. cofiguratio with an added negatme G strap used in test

conditions D and H

304 Awiao Space. and Eiomo wlaMtedzcuw , ApnI. 19%6

NEGATIVE G STRAP EVALUATION-HEARON & BRINKLEY

acceleration of the test vehicle and seat, velocity of the These isolated cardiac conduction disturbances weretest platform, seat loads, and loads measured at the transient in nature and required no treatment Signsrestraint harness attachment points Accelerations at and symptoms of cardiovascular shock have been notedthe head and chest of the subjects were measured by folloN ing- G, impacts exceeding 30-G peak with onsettnaxial translational accelerometers Photogrammetric rates of 1,000 G-s ' or greater (21) The involveddata were obtained by two hsgh-speed motion picture subjects were temporarily incapacitated, but vital signscameras mounted on the test fixture, permitting rapidly improved with recumbencymeasurement of body segment displacements during the Temporarily incapacitating neurologic disturbancesimpact The left-handed coordinate reference system have been observed following experimental and opera-for acceleration (+ X anterior, + Z cephalad) was used tional forward-facing impacts Transient visual distur-during data analysis. bances have been reported after -G. impacts above

Electronic and photogrammetric data were processed 35 G by Stapp (21) and Beeding (2) Reader (16) hasby computer. The Wilcoxon paired-replicate rank noted anecdotal reports of inappropriate crewmembertest (23) was selected to compare the peak values of behavior resulting from presumed concussion duringmeasured parameters and to establish the statistical aircraft crashes and ditchings However, such be-significance of observed trends in the data This havioral disturbances in a laboratory setting presumablyanalytical approach established each subject as his own would be transient and reversible Musculoskeletalcontrol and thereby reduced the effects of biological trauma, in the form of vertebral compression fractures,variability among subjects The 95% confidence level, has also been observed after -G. human impactassuming a two-tailed test, was chosen as the level of experiments One fracture occurred at a peakstatistical significance for analysis of the electronic data. acceleration below 20 G but with a relatively highThe more liberal 90% confidence level was selected for velocity change of 17 4 m. - (12). Other vertebralrejection of the null hypothesis in the photogrammetric fractures have been observed at peak accelerations indata analysis due to the greater variance in these data excess of 30 G with onset rates over 1,000 G-s-' (2).compared to the electronic data Although no neurologic sequelac have been reported as

a result of such fractures, the injuries nevertheless carryEVALUATION CRITERIA the potential for prolonged disability due to chronic back

The evaluation criteria for this study were based on pain or for permanent neurologic damagethe fundamental principles of biomechanical protection In light of these considerations, vertebral compressionIn general, injuries resulting from impact accelerations fracture may limit - G. impact tolerance as well as + G,are due to differential acceleration of body segments tolerance, in spite of the cardiovascular and neurologicor parts and excessive internal structural loading. In effects observed at lower peak acceleration levelsparticular, human tolerance to +G. impacts appears Thus, during forward-facing impact tests, minimizingto be limited by vertebral compression fracture seat loads, which are generally reflective of vertebralTherefore, it is most important during vertical impact loading, appears to be warranted However, probablyto minimize resultant seat load since this load indirectly equal in importance is the goal of minimizing bodyreflects axial loading of the vertebral column Of segment accelerations, particularly head accelerations,secondary importance during vertical impact is that in view of the transient but potentially incapacitatinghead and chest accelerations be minimized because neurologic consequences of excessive head accelerationthe accelerative forces acting on these body segments during -G. impactsmay produce bending and, therefore, reduce the load- Also, for the purposes of this study, the tendencycarrying capability of the vertebral column toward torso submarning during forward-facing impact

During the vertical free fall preceding impact on %,as estimated by measuring displacement of a targetthe drop tower facility, a near zero-G environment is fixed to the subject's knee A side view of theestablished, causing the subject to become "light" in the impact response (photogrammetric data) was used toseat Resultant scat load was used during this period quantify knee displacement from the seat referenceas an indicator of the degree of man-seat coupling axis Relatively large knee displacement was assumedWe assumed that the higher the seat load the better to indicate a greater tendency toward submarining andthe man-seat coupling during free fall. Thus, resultant thus a reduction in knee displacement was consideredfree-fall and impact seat loads and resultant head and to be a favorable finding In summary, the criticalchest accelerations were considered critical response response parameters in the horizontal test phase werep'arameters during the vertical tes, phase. seat loads, resultant head and chest accelerations, and

The mechanism of injury limiting human tolerance resultant knee displacementto -G. impacts is less clear. Medical adverse effects RESULTSinclude cardiovascular, neurologic, and musculoskeletalcmsequences Relative !wadycardia has been reported Selected response parameters from each set offollowing 15-G peak. 6 I m's ' impacts (17). This effect Wilcoxon comparisons are summarized in Tables Ill-VIwas believed to be vagal-mediated since it could be Means, standard deviations, and percentage increaseblocked by the pre-impact administration of the atropine in parameter means are presented tor the peak values(22). Intraveniricular conduction defects in the form of these parameters. In these tables, an asteriskof bundle branch blocks have been noted following designates a statistically signifcant difference in aforward-facing impacts at 11 3-G peak, 14 2 m's (13). response parameter at the chosen confidence level

A.ta!,on Space and F-.,ronmental educdme "April 1986 305

NEGATIVE G STRAP FVALUATION-HEARON & BRINKLEY

Means and standard deviations of all measured and In Wilcoxon comparison C-D, the influence of thecomputed response parameters in these test conditions negative G strap on -G, response in the conventionalhave been presented elsewhere (9) restraint was assessed Findings among the critical

For the 67 tests conducted during the horizontal test response parameters in this comparison were similarphase, the mean peak sled acceleration was 9 48 _t 0.08 to the findings in comparison A-B No statisticallyG with a velocity change of 9.20 -- 0.06 m-s' For the significant changes in resultant head or chest accelera-64 experimental-level tests conducted during the vertical tions were observed. Resultant knee displacement was,test phase, the mean peak carnage acceleration was 9.96 again, significantly higher without the crotch strap. this± 0 06 G, and the velocity change was 8 00 ± 0.05 time by an average of 20%. We, therefore, concludedm-s'. The impact test conditions dunng both phases of that addition of the negative G strap decreased thethe experiment, therefore, were well controlled tendency toward submarming. In this comparison,

vertical seat load was significantly increased in theHorizontal Test Phase condition with the added negative G strap by an average

Negative G strap effects are presented in Table 11. In of 14% While this could indicate that greater vertebralWilcoxon comparison A-B, the effects of incorporating column loading may be anticipated when subjects area negative G strap into the PCU-15/P torso harness and exposed to - G. impacts in a conventional harness withlap belt configuration are examined No statistically an added negative G strap, a portion of the increasedsignificant differences were found in vertical seat load seat load may represent vertical components of negativeor resultant head or chest accelerations However, G strap and lap belt tensions acting through the pelvisresultant knee displacement was significantly increased to the seat. The relative contnbutions of these twoby an average of 11% when the negative G strap was potential effects is unpossible to determine from thenot used in the PCU-15/P configuration Therefore, available data Howeer, the second effect is believedaddition of the crotch strap to this restraint system to predominate purely from geometric considerationsprovides more effective pelvic restraint and decreases Changes in restraint dynamics due to crotch strapthe tendency toard torso submarning during forward- incorporation were also evaluated The total shoulderfacing impact. strap load was significantly increased when the negative

TABLE III HORIZONTAL TEST PHASE NEGATIVE G STRAP EFFECTS

PCU-15/P CONVENTIONAL

CELL A CELL B CELL C CELL DRESPONSE PARAMETER WITHOUT WITH % 4 WITHOUT WITH %4

(n =14) (n 18)

Resultant Head Acceleratmn (G) 174 168 4 167 178 7±t44 ±t44 -L36 ± 54

Resultant Chest Acceleration (G, 246 255 4 16 ! 17 3 7±-4"5 =52 -t22 ±21

Total Shoulder Strap Load (N) 2930 3080 5. 2760 3240 17-±440 t 398 _t449 ±556

Tme to First Peak Shoulder 83 85 2 72 77 7"Strap Load (ls) ±t5 ±4 ±14 ±4

Total Lap Beo Load (N) 8580 9260 8. 7530 8250 10"±L 1230 ±t 1610 ±911 ±t 1240

Time to Peak Lap Bea Load (ms) 72 74 3" 70 70 0±-4 ±t4 ±-4 t3

veriical Seat Load (N) 6690 6810 2 5940 6860 14*±-1040 ±t 1290 ±892 t1350

(n 10) (n 15)

Resultant Knee Displacement (otn) 248 224 i1.. 237 197 20-± 35 "t 34 t5 3 ±4 1

Data presented are means ± S D for maximum accelerations. loads and d.splacemaents and for sin to mnXXinum strap loads'Means are statistically different by the Wdcoxon paired-rplicati rank test (2a !0 05)"*Means are statitically different by the Wilcoxon paired-replicant rank test (2a ±0 I)n = number of matched pairs Value of n is different for photogrsmmernc data due to pariat data loss

306 Atsaron, Spa"r, and EDmironmenelMedicme - Aprd. 1986

NEGATIVE G STRAP EVALUATION-HEARON & BRINKLEY

G strap was added to either restraint configuration The may have been anticipated because of the direct physicalpercentage increase in this load was larger for the con- connection between the torso harness and the negativeventional harness than for the PCU-15/P configuration G strap, the reason for the increased lag appears toThese findings may have been anticipated on the basis be more complex. The time history of the shoulderof geometric considerations Addition of the negative strap load in the conventional harness was biphasic;G strap to the conventional configuration establishes a i e., it had two peaks The amplitude of the first peakdirect load path from the shoulder straps to the seat, was higher in 12 of the 18 tests when the negative Gthereby improving the load-carrying capability of the strap was not used (test condition C). However, it wasshoulder straps In the PCU-15/P configuration, on consistently higher when the negative G strap was usedthe other hand, there is no direct physical connection in test condition D Therefore, incorporating a negativebetween the added negative G strap and the torso G strap into the conventional restraint appeared toharness Nevertheless, the total shoulder strap load was increase the amplitude of the total shoulder strap loadstill significantly higher with the added crotch strap than and the time required for that load to reach its peakwithout it, probably due to the more effective pelvic value.restraint provided by the crotch strap accompanied by an The total lap belt load was also significantly increasedincreased forward inertial response of the upper torso when the crotch strap was used in either restraint

The time to peak shoulder strap load was not configuration These increases may be attributed tosignificantly changed when the negative G strap was the associated increases in shoulder strap loads in testadded to the PCU-15/P configuration However, the conditions B and D.time to peak shoulder strap load was significantly The differences between the two restraint systemsdelayed by an average of 5 ms when the negative G strap observed in the forward-facing tests are presentedwas added to the conventional double shoulder strap in Table IV. In Wilcoxon compansn A-C, the twoand lap belt configuration Though the latter finding restraint systems without added negative G straps were

TABLE IV HORIZONTAL TEST PHASE RESTRAINT CONFIGURATION EFFECTS

WITHOUT CROTCH STRAP WITH CROTCH STRAP

CELL A CELL C CELL B CELL DRESPONSE PARAMETER PCU-15/P CONV %4 PCU-I5/P CONV %

(n= i5) (n N4)Re)'tan:i Head Accekeraton (G) 170 16 7 2 i 3 .82 12"±37 ±t:35 ±41 ±56

R-•e-.tnt OCest Acceleraton (G) 245 16 2 51 262 17 3 51i±51 ±t24 ±51 ±-20

Total Sh-uider Strap Load (N) 2990 2700 It1 3120 3140 <1±;30 ±--404 ±420 ±439

Time to First Peak Shoulder 85 73 16" 85 77 10"Strap Load (m) to ±16 "t4 = 5

Total Lap Belt I..; (N) 8540 7530 13' 9310 8300 12,"4-1260 ±-790 ±1590 ±1290

Time to Peak Lap Belt ( .,,'Qnc 72 70 3 74 69 7-44 f4 ±4 -t3

Negasve G Strap Load (N) 604 945 56"±229 t 359

Time to Peak Negate.. G Strap 243 117 105*Load (nu -t 26 ±L 37

Vertcal Sca Load (N) 6590 5940 111 6790 6740 <1"4-1060 ±876 .1290 ±1350

(n = ) (n= 12)

Resultat Knee Displacement (om) 24 8 240 3 23 4 206 14"±460 ±t 53 ±343 =29

Data presented are means ± S D for maximum accelerations, loads, and dsplacnmcnts and for taie to maximum strap loads*Means are sutatx.xally different by the Wdcoxon patred-rep•Cate rank test (2 at 40 05)**Means are statiasally different by the Wdtroxon parred-rephicate rank test (2 a •0 I)n = number of matched parts Value of n is d.fferent for photogrammemic data due to partal data loss

Aviaton Space. and Emrotnmental.Medtarx April. 19&6 307

NEGATIVE G STRAP EVALUATION-HEARON & BRINKLEY

compared. Vertical seat load was 11% higher for finding was expected since a portion of the shoulderthe PCU-15/P configuration than for the conventional strap load was carried via the negative G strap to the seatconfiguration. This finding may be related to increased structure Also, the peak negative G strap load occurredlap belt loads rather than increased spinal loads. Also, 108% later in the PCU-15/P configuration comparedthe resultant chest acceleration was 51% higher for to the conventional configuration. This longer delaythe PCU-15/P configuration. However, no statistically until peak tension in the negative G strap is consistentsignificant difference was observed in resultant head with the interpretation that the PCU-15/P configurationacceleration nor was there a significant change in permitted more movement of the pelvis during impactresultant knee displacement. The latter finding suggests than the conventional configuration. This finding is alsothere is no difference in anti-submanning performance in keeping with the greater resultant knee displacementbetween the two restraint configurations Nevertheless, seen in the former condition.we concluded that the PCU-15/P configuration is inferiorto the conventional harness by virtue of the chest Vertcal Test Phaseacceleration and seat load findings The significantly The negative G strap 'ffects observed in the verticallower chest acceleration measured in the conventional test phase are summari.ed in Table V Results ofconfiguration indicates superior coupling of the upper adding a negative G strap to the lab beh used withtorso to the seat structure by the two shoulder straps the PCU-15/P torso harness were obtained in Wilcoxonwhich are directly linked to the lap belt in that comparison E-F Resultant free-fall seat load wasconfiguration. significantly higher when the crotch strap was used,

In comparison B-D, the two restraint configurations indicating better man-seat coupling during the free-fallwith added negative G straps were compared No phase of the experiment In addition, resultant impactstatistically significant difference was observed in verti- seat load was significantly lower with the added negativecal seat load or resultant head acceleration However, G strap, suggesting less vertebral column loading ofresultant chest acceleration was significantly higher in the subjects during impact Resultant head and chestthe PCU-15/P configuratioi titan in the conventional accelerations were not significantly different in theconfiguration. In addition, resultant knee displacement two test conditions On the basis of these data, wewas significantly larger in the PCU-15,P configuration, concluded that incorporation of the negative G strapsuggesting a greater tendency toward torso submann- improved the vertical impact protection performance ofing In summary, analysis of the critical response the PCU-15/P torso harness and lap belt configurationparameters in comparisons A-C and B-D revealed that In comparison G-H, the effect of adding a negativethe PCU-15/P configuration provided less adequate G strap to the conventional configuration was assessed.forward-facing impact protection than the conventional Similar findings among the critical response parametersconfiguration, whether or not the negative G strap was were seen in this comparison insofar as resultant free-used. fall seat load was increased and resultant impact seat

Analysis of the strap loads and times to peak strap load was decreased when the negative G strap wasload provided additional supporting evidence for this used However, the magnitudes of the changes in theseconclusion Total shoulder strap load was significantly parameters were significantly greater in this comparison,higher in the PCU-15/P configuration compared to the indicating that the negative G strap had an evenconventional configuration when the negative G strap greater beneficial effect when added to the conventionalwas not used in either restraint system (comparison A- configuration compared to the PCU-15/P configurationC) However, when the negative G strap was added This conclusion was also supported by the findings thatto both configurations (comparison B-D), no significant resultant head and chest accelerations were significantlydifference was observed in the total shoulder strap load less when the negative G strap was added to theThis is probabl) due to the large increase in shoulder conventional configuration. In summary, analysis of thestrap load associated with adding the negative G strap critical response parameters in these two comparisonsto the conventional configuration since a direct load revealed that adding the crotch strap to either restraintpath is established from the shoulder straps to the seat system improved man-seat coupling during free fall asvia the negative G strap In addition, time to peak well as the vertical impact protection performance of theshoulder strap load was significantly greater for the restraint system.PCU-15/P configuration whether or not the negative G Restraint dynamics were elucidated by f rther studystrap was used These findings are consistent with the of the available data in these two comparisons. Ininterpretation that the PCU-15/P configuration permits comparison G-H, addition of the negative G strapgreater displacement of the upper torso from the seat dramatically reduced the total shoulder strap load atbefore the subject is effectively restrained impact This reduction was believed to be due to better

In both comparisons, the maximum lap belt load mechanical coupling of the upper torso with the seatwas significantly higher and occurred slightly later in structure during free fall of the impact carnage by virtuethe PCU-15/P configuration than the conventional con- of the direct load path from the shoulder strap tie-downfigurations These findings also indicate the relatively point to the negative G strap tie-down point in thispoor performance of the PCU-15/P configuration configuration On the other hand, when the crotch strap

Finally, in comparison B-D, the maximum negative was added tc the PCU-15/P configuration (comparisonG strap load was 56% higher in the conventional E-F), the total shoulder strap load was not significantlyconfiguration than in the PCU-15/P configuration This changed This finding is consistent with the fact there is

308 A vuzfon, Space. and Em conmenmal Mediae *ApnL. 1986

NEGATIVE G STRAP EVALUATIGN--HEARON & BRINKLEY

TABLE V. VERTICAL TEST PhASE NEaATIVE G STIAP EITFC )S

CMtLF CEL. F CE*UG CELL P

RESPONSE PAISAMETritR WITHOUT WITH % 4 WITi±oUT WITH %

(n 151 (n~ iS)

Resultant Head Axeleravon (3) 133 13 - i. 128 120 7-±12 ±J8 t±"9 -09

Resaltat Chest Arejerano (G) iS98 165 152 9.t:,±2 ±12 ti10

Toal MISolder Strap Load (IV, 429 *A4 3 327 168 93.±132 t±13( ±166 ±203

rme to Peak Shoulder W 7- 1 81 97 20-Strap Loadn) ±l! -it ±10 ±12

Total Lap Belt Lead (N) 4,' 394 25' 359 378 48-='~ '22 t±177 ±106

Tite n sPeak Lap Blet Load (wa) 6ý 70 3 73 7A I!O 4 ±13 ±14

Rttilmiet Fret-Fall Seat LoaJ 'N) 112.5 124., 13* 1210 1820 so..t±20 ± 306 ±363 ±,t478

Resultant lespat Seat Load (N) 9950 M' 3' 840 790D 6-:it 10 :L 100 ±987 ± 1050

Data presented oa means t S D for t=a LM:n a2ti.'r Z005. k'ids. nýd for timle to inasmurn Strap loads*Means U~e vaslattalt, drfferent b, h 'A~ M~iexi oul.. _- 1-.pttrae rank t=s (2a 10 05)

n = n=-rr of matclued pints,

no direct connection betIween th.2 sho'ti..e Straps of the fall and less adequate vertical impact protection than thePCU-Is'/P torso harness sod m'e i;p t'ea w~tl ain ad

tded conventional restraint.

negatise G strap, Vertical impact response differences in the twoT'he time from the sta.t 2sf imphct to r.sa~i: ium' re-straint systems with added crotch straps were assessed

shoulder strap load was increased siginicarsly when in comparison F-H Based on similar findings amongthe negative G Strap was adice tc: rt e con-yenticnaw the critical response parameters, we drew the saneconfiguration (comparison 0-11). TI.týs nine 5 itft cesickisions as in comparison E-G Resultant free-fallappears to be due to the r-nare r-.ationship, l.'twe-n seat load was significantly greater and retultant impactthe negaive G strap loa' ar at the sesc'uldzr strsp loads seat load was significantly lean in the conventionalrather than to a zhange iai :he stiffne-s- it the restraint configuration. In addition, resultant head and et~estconfiguration acz)elerations were significantl" less in the coniv.-rtional

In both comparisons, thr Uip M2t ioatsi were configuration compared to the PCU-151P? configuration.significantly higher withou' ,be is 'ative G strap TIhest Finally, the dramatic differences in shoulder strap leadfindings are consistent 'vith it.-! f;;ct th.'z the nega'ive 3uid negative G strap load seen in comparison F-HG strap shares the loads reqcett-d 'o restrrjn the pe~vis, demonstrate the effectiveness of the direct load pathwhich arc generally caqied 's, the LF: be~t. fr.m shoulder strape to seat via the crotch strap in test

Differences betweor. the- two mcrtraiat u-isternis in tie condition H The maximum tension in the negative Gvertical lest phase are sht's' in tabiz VI If- kilcoxon strap was significantly greater and the max'unum load atcomparison E-G, th.- resulta-it crewst a -celeeration and the shoulder strap anchor point was significsijtly less intotal shoulder strap lond were. s~gnilsrcintly muitced in the zinventional configuration compared to the PCI)-tem consvenstional configssrazion -,oetzrirc 4

to (216 PCI2. 15/P wrnfiguration15.,P configruratitin. ?&, sigi.tkiutt chansz wasm ohs-.rved MEcCUSSIQNit, resultant head accal-rarion. Fnially, toe roaitszanfree-fafi t eat load was vignificrt-..y ilter zetd wn.'e the These tests demonstrated that negative G ýtrap ine'tr-resultant imFact Ses't ioad WaS SignifiCdtt.:.' JPv~e2Sed psration into the PCU-I5/P confi3 uration or the conven-in the conventional cunrfi;!ration ccompared to the ional configuration reduced the tendency toward t'srsoPICt-1-15/P cssrnfigration Thcst tri~ngs a-e ecncsstz~t submarimng during forward-facing impact, impro.edwith the interpretation th't the 14X-1.1? ~onfieurar,,n tiecuipant-seat coupling during free fall, and improve~dprovides relatively ooor wan~rrat ;c'sipLn; during free teitical impact protection During the forward-facing

Avtar`ýt space and EnrasnmnentalMed&cm- Aprt', 184 309

NEGATIVE G STRAP EVALUATION-HEARON & BRINKLEY

TAILE VI VERUhCAL TEST PHASE RESTRAINT CONFIGURATION EFFECTS

WITHJOUT CROTCH STRAP WITH CROTCH STRAP

CELL E CELLOG CELL F CELL H

RESPONSE PARAMETER PCU.15/P CONIV %6 PCU.15/1P COWy %4

(n 14) (n 16)

Resultant Head Aceleeration (G) i133 '.Is 4 12 9 121I 7-±13 ±09 ±0 9 ±0 9

Resultant (lest Acseteration (G) 199 166 20' 19, 154 24*±t2l ±19 ±.25 ±12

Totl! Stitilder Strap ..od (N) 46Y 365 54' 473 179 164'-t139 ±141, =143 ±17

Tim to Peak Shoulder 82 81 1 90 97 1Strap Load (ms) ±t c ±10 ±t1I1 1t2

Total La, Bill Load (N) 517 55' 7 413 361 13±8 L WI3 t 119 ±t112

Time to Pak Lp Belt"ad (ms) 68 72 4 73 73 0_i:5 1:12 ±1l' ±15

Negative G3 Str'p Load (N) 181 448 148*:L 76 ±114

Titm to Peak Negair e G Smrnn 117 129 6"Lnd (mn) ±t28 ±14

Resuttamt Free.Fali -2al Load (N) i080 1230 141 1259. 183 46'± 234 ±371 ±L3.'S ±t46S

Resnltetnt Inmpaet Seat Load (H) 9130 8400 9. 87"' 7850 Il'±1110 ±1020 :L118() ±t1040

Data presented are means ± S D for tnaxmnam aerelerations. ittad, a.W for iton to maximum strip loads*Means a-e statistieati diferent by ,he Wileoxon ý,aed-rephieat rank test (2. stO( 113)r. numuber of matehed 9si.-

impacts, negative G Strap incorpuration produced raj from dicreaied upward rotation of thte lap belt Inaduersi. changes ~mong crittca! response parargeters tn some restraint conftgi-raiions. notably the conventionalthe PCU-15/P conifiguration and or.iy ratsed the question restrain, used in this study, the negative G strap l-nksof possible performance degradat-cn in the conventiona; the shoulder straps to dhe :ower seat structure, thc~rebycon.iguration Nj medtc~l contraind'cationk to stegative permitting shoulder strap loads to be carried directly too strap incorporation we~re founo in this study. the seat

In a concurrent stuty, perforrn~d on the AFAMRL In the imp5.ct context, the primaiy perceived benefitDynamic Environmert Simulat-)r, negative G strap of neg.tire G strap incorpor.,tion is to decrease theaddition to the PCU-13,'P configuration w-is shown to likelihood of torso submnarning under the lap belt duringhave a ber-,ficial effect in a suatamned - 2.0 G. envtron- -G, impact acceleration By tethering the lap belt toment. 0.ithough no statistically signtficatit d-.fferences i.a the lc'wer ,eat structure, the negative G strap reducestrackir-g tz-sk perfjrmance v.e,e icsino, subiscct vertical the tendency frr the lap belt to rotate up and over thedtsp!?cement frorn the seat mas significantly less when anterior superior iliac spinies of the pzlIvls. During suchthe nie-,ative G strap wa uased (10) Rcduced vertical forward-factng impacts, shoulder stiap loads may also bedispiacem-nt rom the seat during sustaimed - G, carrtid to the lower seat structure in a manner similaracceleration has alszs been observed when a cr,,tch strap to the sustained -G. case. but the origin of the -G.was added to tlse U S Navy MA.I. torso harness (11) ioading is different and the load magnitude is greatly

In asse'.alg the utility of negative G or crotch increasedst.-ap incorporation into various restraint systems, it is The perceived risk of negative G strap Incorporationusefull to consider tha. the nc-gative G straps functions iýprimnarily the potential for injurý of the groin Orseparately !n the operational and .mpact centexts. genital-a during a - G. inmpact associa.ed with electionl

In the operations! context, 1.he perceived c:.er benefit or aircraft crash. Avoiding significant submarining inof negative G strap incorporation is the improved such c~ises is essential to prevent loading of the anteriorsuppoAt during - G. acceleration maneuvers resulting abdomrinal wall by the lap belt and, therefore, the risk of

310 Arstmon, Space. anid Eiiion~ni ~eAfedicnie April, 19846

NE~GATIVE C STRAP EVALUATION-HEARON & BRINKLEY

significant internal injury. A correctly designed restraint not a negative G strap is used In the conventionaldoes not prevent qubriarining by the application of configuration, there is better integration of the lap beltdirect negP,.tive G strap lsvasing of the genitalia or groin and shoulder straps, addition of the negative G strapNevertheless, sos-h loading is conceivable, particularly provides a direct load path by which shoulder strap loadswith a loosely, ad~u,,^rd lap belt or ar ,riferior negative G may be carried to the seat structure On the otherstrap attachir-ent located 'too far aft forr the crewmember hand, in the PCU-15/P configuration the lap belt within qiie~ston or without the added negative G strap is not directly

Linited ojs-rationai expenerýce with crotch straps has attached to the shouldcr straps of the torso harness Thebeen 3ccrised in fosreigo mdithar- reivicrs, notably the relats'ely poo: integration a-niong the restraint strapsUnited Kingdom, and in thiz T-38 aircraft previously catses the PCU-15/P configuration to be a relativelyu~ed as USA,'ý Thun-Serbirtis Thic most extensive poo)r impact protection devicc. This is not surprisingUSAF operazional expe.-.ance with a restraint h-arness uince the syst,:m was originally designed to functiosn as aw.0ic% incorp--pites a neg.-ittse G strap bas beer! with parachute harness Additional research at AFAMRL isitae harness .f the F.Th-t11. Although ejection in progress to identify restraint harness features whichexperterev in the FiFB-111 has been associated with a may further improve the performance of curreist as wellre-lativ,,I, high rs'tr ot ventet'al frac:turp among survived as future USAF restraint systemsecjecteits. ejectson-rslstst injuncst do not commonlyinclude les;osss of bhe groin or Lanitalia (7,8). Onlyoie scrotal laceratiorn and two thiu&h contusions maybe attributed to the presence of tlie nestative G strapin the F/-?B-111 restraint system. The ciewmember ACKNOWLEDGMENTSwho in~u'-ed a 5-cni scrotal laceration alsoi suffered We are gratefusl to members of the Bioomechasscai Prostectiosmultiple vertebral fractises during a nevar nosse-down Branch of AFAMRL weho particnpated io she ptassseg, preparationlanding impaict of the crewv module resulting from a and imoplementation of these experiments Special thanks is given to

Capi Thomas Jennings, ILi David Hudson, CMSgt i wsizm Saylor,failure of the parachntsi suspension system. The ejection Ma~ft Dale Schummel. SSgt Jimmy Berry. and Sgi Dasiel Beachydala, thrceteore, suggest that thj FIFB-1 11 crot'-h strap tor these invaluable nsssstansce during tihs lest progranmfuf.ctio-ia V'ithOi~r rroducing signif~cant injury to the The itmpact fW lsies and data collesison eqsuiptnent were masntasnedgroin or genitalia Furthermore, extenarte human and operated by the Sientisfic !ervces Dsvisson of the Dynatectron

imattest of the F/FBI111 restraint sytm wt Corp under USAF Cosntract F33615-79-C-0523 Thanks so allimpat e - ssemcontractor persotnel, partiscularly Mes~sr Harold Boedeker. Rtobert

the shoulder strap aiicl'or pssin slightly modified) in Flannery, and Steven Masher for their oststanding support durnog thisall thr-ee cardinal axes h'ave not been assosntued with research effootclinica~y signrfcarit problems in this region (3)

Nevertheless, we cannot quantitatively predict theoperational injury potertial associated w;th negativeG strap addition to the PCU-lSIP torso hamness andlap belt configuration, for exaemple We presume REFERENCESthat the greatest likelihood for injury in an open I Baton R Atecrew personnel restraint subsystems; definition otejection seat is during transient - Gx accelerations deficencies and reqmirements Patuxsent Rsver, MD Ate Testresulttng from seat decele-ation with droguse parachutes Center, 1978, NATC-SY-28R-78or fto)m aircraft crash lanadtng All indications from 2 Beedsng EL Daisy decelerator tests 520-707 (i3 July 1959 -the relevant operational and experimental data are 13 April i960) Hotiomnan AFB. N1 4 Ate Force Misssilethat operational injuries of the groin or genitalia due Dveloipment Center, 1960, MDW Test Peport No 60-4

3 Brnkhley SW. Raddin 3M Jr. Hearon BF, McGowoan LA. Powrersto negative G strap incorporvison will ha unlikely 3M Evaiuations of a proposed. modsfied FIPB-111 crew seatFurthermore, those injureie which do occur are likely and restraint system Wrsght-Pattersont AFB, OH Aire Forceto be clintrally inconsequential or to be associated Aerospace Medical Research Laboratory, 1981, AFAMRL-with unrelated hot racre serious sn)uries in other organ TR-55-52

4Destardism SF, Lainaneni OH Asrcraft crash sursival dessgnsystems. These conclusions are predicated on the gusde-.Volumne IV Fort Eustio. VA Unitied States Armyconsisttent proper adjustnient arid pretenstoning of an Research and Technoiogy Laboratories (AVRADCOM). 1980,appropn-ately designed restraint system USARIL-TR-79-22D

On the basis ef the these test results and other 5 Fryer Di Operational espenience nwith British ejection sears aavailable evidence, sufficient benotits ap rtoderive survey of medical aspects Faroborough. Hants. UK RAF

apper toInstitute of Aviation Medhane, 196i. FPROI 166from use of the negative G or crotch strap to 6 Hearon BF. taiddrn JH Ir Expenience noith highiy telectssewarrant a recmmendation for its incorporation into screening techniques foe aceleration sirens duty Inselected USAF restraint systems, notably the PCU- Proceedings of AGARD Conference on The effect of long-term15.11" torao haraiess and lap belt configuration Design~s therapeuticsc, prophylaxis and screening techniques on isrerew,

medincal standards. 1981, AGARD-CP-310for incorporation should be based on knowledgeable 7 Hearon BF F/PB-Ill ejection exponence (1967-1980)--Part 2exploitation of potentiall benefits and avoidance of Summary of accident investigation reports Wright-Fatiersonpotential hazards AFB, OH Air Force Aerospace Medical Research Laboratory.

Finally, the conventional double shoulder strap and 191 AFAMRL-TR-81-114lap belt restraint is clearly preferable to the PiCU-15/P 8 Hearco BF. Thomas HA, Riddin JH Jr Mechaninsm of vertebrai

fracistre in the F/PB1-I I ejection expenience Assai Sparetorso hariess and lap belt configuration as a forward- Enstron Med 1982. 53 44048facing or vertical impact protection device, whether or 9 Heaton BF. Brinkley J5

5e Huosont DM Sayior WJ Effects of

Arsasos, Spame, aiid &Esvru.ninentsalMedicsm - Apnl. 1986 311

NEGA11VE 0 STRAP EVALUATION-HEARON & BRINKLEY

a negative G strap on restraint dynamics and htuman inpact Aviat Space Envtron Med 1979, 50 267-70responte Wctght-Patterson AFB, OH Air Force Aerospace 17 Rhein L, Taylor E Relative bradycerdia after ampact HollotnanMedical Research Laboratory, 1983, AFAMRL-TR-83-83 AFB, NM 6571st Aeromedicat Research Lahoratory, 1962,

10 Lenpp DO ACES 11 negative G, restraint investigation (master's ARL-TR-62-12thesis) Wright-Patterson AFB, OH Air Force Aerospace 18 Rice EV, Brady JA, Van Dyke RS The rote of personal restraintsMedical Research Laboratory, 1983, AFAMRL-TR-83-49 at Navy ejectton seats In Proceedings of SAFE 13th Annaal

11 Loech D Centrifuge tests of modifications to the MA-2 Conference and Trade Exhibit, 1975, 58-61.aarcressntan torso harness-Phase! Warminsler, PA Naval Arc 19 Schatl DG Noo-celction cervical spate fractare due to defensiveDevelopment Center, 1982, NADC-82126-60 aerial o bntha maneuvering in an RF-4C a case report Aviat

12 Lovelace R. Baldes E. Wulff V The ejectioni seat for emergency Space Environ Med 1993, 54 1111-6escape from high-speed aircraft Weight Field, OH Air 20 Shaffer ST The tmpslse accelerator an impact sled facility farTechnical Service Command, 1945, Memtoranduat Report human research and safety systems resting Weight-PattersonISEAL-3-696-74C AFB, OH Aerospace Medical Research Lahoratory, 19176,

13 Majewikiu P. Borgmaa T. Thomas D, Ewing C Tramsient in- AMRL-TR-76-traventricalar condsiction defects observed durnog experimental 21 Stapp JP Human txposures to latear deceleration pact 2- Theimtpact in haatan subjects In Proceedings of AGARD forward-facmag position and the development of a crash haeinessConference, 1978, AGARD-CPP-253 Wnght-Patterson AFB, OH Weight Air Dcsclopmeut Center,

14 Reader DC An assessmtent of an alternative restraint harness for 1951, AF Tecinn-al Report No 5915. Part 2the Chipmunk trainer Farnboraugh, Hants, UK Royal Air 22 Taylor E, Rhein L, Beers G Effect of atropine Lopn the relativeForce Institute of Aviation Medieine, 1969, Report No 475 bradyrardia associated with impact Hollonma APB, NM

15 Reader DC A case for sthe negative-G Strap In Proceedings 6571st Aeramediral Research Laboratory. 1962, ARL-TDR-of AGARD Conference on Linear acceleration (impact type), 62-131971; 88 C4-1 to C4-3 23 Wilcoxon F. Wilcox RA Some rapid approximate statistical

16 Reader DC Head acceleration and paydsomotor performoance peocedures Nesw York Lederle Laboratories, 1964

NTIS Gli -

Av-2'i :-lit- Codes_,ail anfd/or

Special

312 Aviation. Space. aid Environmentaal Medicate Apedl. 1986

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Ca•parison of Hmm im~act Response in Restraint Systemns With and Without a Negative G

12 PERSONAL AUTHOR(S)B. F. Hearon and J. W. Brinkley

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